Oct 14, 2011 RPG Meeting Cross Valley Brownsville Loop Project – Status report

2 Oct. 14, 2011RPG Meeting Project Options Option 1 – (Sharyland and BPUB proposal) New 345kV Loma Alta station with two (2) 345/138kV 450 MVA auto ~14 mile 345kV transmission line from existing 345kV La Palma station to new 345kV Loma Alta station ~59 mile 345kV transmission line from new 345kV Loma Alta station to new 345kV Frontera station across the valley Option 3 New 345kV Loma Alta station with one 345/138kV auto ~25 mile 345kV transmission line from existing 345kV RioHondo station to new 345kV Loma Alta station Rebuild LaPalma-Cavazos-Military Highway with ACSR Rebuild LaPalma-Los Fresnos-LomaAlta with ACSR

3 Oct. 14, 2011RPG Meeting Project Options (Cont.) Option 4 New 345kV Loma Alta station with one 345/138kV auto ~25 mile 345kV transmission line from existing 345kV RioHondo station to new 345kV Loma Alta station Rebuild and convert LaPalma to Brownsville 69 kV line to a 138 kV line; Add new 138 kV substation to tie LaPalma- Brownsville and the Military Highway-Carbide138 kV lines. Option 5 (new) New 345kV Loma Alta station with one 345/138kV auto ~25 mile 345kV transmission line from existing 345kV RioHondo station to new 345kV Loma Alta station ~12 mile 138kV transmission line from LaPalma – Palo Alto

4 Oct. 14, 2011RPG Meeting LRGV/Brownsville Area Transmission system Rio Hondo-Loma Alta 345 kV for Options 3, 4 & 5 LaPalma 138 kV rebuild’s Option 3 LaPalma 69 kV to 138 kV Option 4 LaPalma- Palo Alto 138 kV Option 5

5 Oct. 14, 2011RPG Meeting Base Case Model & Assumptions YTP summer peak case based on the 2011 SSWG Dataset B Brownsville Area Load ~ 589 MW (including 250 MW load at Loma Alta) Silas Ray largest combined cycle unit (train) turned off Silas Ray oldest unit (49 years) turned off Total generation online in Brownsville ~ 48 MW AEPSC LRGV Project o A new 163 mile, single circuit 345kV line from Laredo Lobo to Rio Bravo to N. Edinburg o Reconductor the existing two 345 kV line in to the LRGV

6 Oct. 14, 2011RPG Meeting 2016 Power Flow Results N-1 & G-1 (with the new 250 MW load) Base Case thermal (n-0) violations in 2016 Rio Hondo – East Rio Hondo 138 kV line (151.6%) East Rio Hondo – Central Avenue Sub 138 kV line (140.4%) LaPalma – Los Fresnos 138 kV line (124.6%) LaPalma – Cavazos line 138 kV (115.3%) Loma Alta – Los Fresnos 138 kV line ( 109.1%) Military Highway – Cavazos 138 kV line (108.3%) There are additional overloads under contingency No low voltage violation (in base case or under contingency)

7 Oct. 14, 2011RPG Meeting 2016 Power Flow Results N-1 & G-1 (without the new 250 MW load) Base Case thermal (n-0) violations in 2016 Rio Hondo – East Rio Hondo 138 kV line (108.9%) There are additional overloads under contingency (as shown in the map) No low voltage violation (in base case or under contingency)

8 Oct. 14, 2011RPG Meeting 2016 Power Flow Results N-1-1 (without the new 250 MW load) Prior Outage of either the Ajo-Rio Hondo 345 kV or Rio Hondo-N. Edinburg 345 KV: The loss of the next 345 Rio Hondo would cause severe overloads on several 138 kV and 69 kV lines (cross valley lines serving Brownsville area). Some of the major post-contingency (> 120%) N-1-1 overloads: Weslaco Unit to Steward Road 138 kV line (158.4 %) Weslaco Switching Station to Weslaco 138 kV line (149.7%) Aderhold to HEC Energy Center 138 kV line (142.7%) Heidelberg to Weslaco 138 kV line (134.0%) Elsa to Aderhold 138 kV line (133.6%) Burns to Heidelberg 138 kV line (126.3%) South McAllen to Las Milpas 138 kV line (124.5%) Wesmer to Weslaco Unit 138 kV line (120.7%) Mitigation plan to prepare for this next contingency (under system peak conditions) would require load shed in the East Valley/Brownsville area. Based on this study, it is estimated that under the 2016 system peak system conditions, it would require ~ 430 MW of load shed in the East Valley/Brownsville area to relieve all N-1-1 overloads.

9 Oct. 14, 2011RPG Meeting Summary of Results √ - no criteria violation x – criteria violation OptionsProject Description N-1+G-1 CriteriaN-1-1 Criteria without 250 MW loadwith 250 MW loadwithout 250 MW loadwith 250 MW load 1 LaPlama - Loma Alta 345 kV & Frontera - Loma Alta 345 kV√√xx 1a LaPlama - Loma Alta 345 kV√xxx 1b Frontera - Loma Alta 345 kV√xxx 3 RioHondo - Loma Alta 345 kV, Rebuild LaPalma-Cavazos-Military Highway & Rebuild LaPalma-Los Fresnos-LomaAlta√√xx 3a RioHondo - Loma Alta 345 kV√xxx 3b Rebuild LaPalma-Cavazos-Military Highway√xxx 3c Rebuild LaPalma-Los Fresnos- LomaAlta√xxx 4 RioHondo - Loma Alta 345 kV, Rebuild and convert LaPalma- Brown 69 kV to 138 kV√√xx 4a RioHondo - Loma Alta 345 kV√xxx 4b Rebuild and conver LaPalma- Brown 69 kV to 138 kV√xxx 5 RioHondo - Loma Alta 345 kV, LaPalma-Palo Alto 138 kV√√xx 5a RioHondo - Loma Alta 345 kV√xxx 5b LaPalma-Palo Alto 138 kV√xxx

10 Oct. 14, 2011RPG Meeting Project Options for N-1-1 Criteria Loma Alta-N. Edinburg 345 kV instead of the Loma Alta-Rio Hondo 345 kV for Options 3, 4 & 5

11 Oct. 14, 2011RPG Meeting Study status/update Completed the studies for the N-1+G-1, N-1-1 and new 250 MW load sensitivities. Working with TO’s to obtain cost estimates for the options. Working on completing the draft study report. The tentative date for the study report is end of October or first week of November.

12 September 17, 2010RPG Meeting March 12, 2010 Questions?